Visual Observations as Exercises in Physics

Visual meteor observations are a fun and interesting approach to astronomy and to scientific research in general. It can be used for laboratory or practical exercises in physics at high schools and universities. The students can personally collect and analyze the acquired data. The output consists of Zenithal Hourly Rate (ZHR) values, spatial density and population index. In this paper, the so called counting method is described as it is the most suitable method for beginners. As a practical example, the ZHR curve of the Lyrid meteor shower was evaluated and the maximum and the duration of the shower were calculated.

The Leonids and the Comet:- History and Theory

The recorded history of the appearances of spectacular Leonid displays have been discussed for example in Yeomans (1981) and also in other papers at this meeting. The similarity in the orbits and that of comet 55P/Tempel-Tuttle is a strong indication that they are related. Further proof of this comes from the fact that the most spectacular displays associated with this stream are seen at time intervals that are multiples of the orbital period of the comet. The explanation for the occurrence of storms is thus that a well populated group of meteoroids are located close to the parent comet. Such a grouping of meteoroids would be formed if the comet were still active, not an unreasonable assumption. However, this raises an other question, namely why have the older of these meteoroids ejected perhaps several thousand years ago, not spread about the orbit. Standard models (eg Williams 1992) suggest that in 20 or so orbits meteoroids will have spread all the way from being close to the comet to being at the opposite point of the orbit. Hence, meteors in similar numbers should be seen every November coming from the Leonid stream. This is not the case, the average zenithal hourly rate of meteors in non-storm years being less than 10 as opposed to several thousand during a storm.